"Recently, Brendan and I have been arguing about what can reasonably be expected from a multi-monitor OS (among other graphical stack things). We've reached the conclusion that nothing replaces real-world user data. So anyone interested, please answer this survey about multi-monitor setups and expectations ! (Results will be published here once the amount of answers has reached a steady state, I'd say in a month at worst)" (Source)

Originally I was planning on getting three 22" (or so) 1080p monitors and stacking them vertically. But ultimately decided on going with one 30" (2560x1600) and one 22" (1080p resolution), as it's enough space for me plus watching movies is better than on one 22" monitor and rotating it back to horizontal.